code: def test_cache_readonly_preserve_docstrings():
      # GH18197
      assert Index.hasnans.__doc__ is not None
  
imports: import numpy
  import pytest
  from pandas._libs import Timedelta, lib, writers
  from pandas.compat import IS64
  from pandas import Index
  import pandas._testing
label_desc: Use image node_id 1 for calling a global function with example usage: test_cache_readonly_preserve_docstrings() without return types